Conventional manual transmissions use gearshift systems whereby the driver manually selects the desired gear by shifting a gear stick into a certain position in the gearbox. The gear stick is in direct connection with an internal shift mechanism usually comprising some form of shift rails, shift forks and shift collars. One disadvantage of such a system is that the gearbox and the gear stick have to be arranged in such a configuration that all components can easily be interconnected by a mechanical linkage. To allow for a more flexible installation, systems have been developed wherein the mechanical linkage has been replaced by a system wherein electro-hydraulic solenoids direct oil to and from pistons mounted at the end of the shift rails to control the position of the shift rail. A well known problem associated with such a system is the locating and securing of this shift mechanism in a neutral position. The positive neutralisation of a mechanism is essential to prevent erroneous gear engagement and multiple gear sets being engaged simultaneously. A failure to do so could result in uncontrolled machine behaviour and severe mechanical damage. Previous arrangements, such as for example the 5-speed Power Synchro gearbox of Turner Powertrain, Wolverhampton, UK, utilise a multiple piston set-up whereby a set of compound pistons operate on hydraulic principles to neutralise the shift rail. This arrangement has certain disadvantages such as the complexity of the components and machining procedures and hence cost.
It is an aim of the present invention to solve one or more of the problems set forth above.